The invention relates to reference weights for electronic scales and more particularly to apparatus for depositing and lifting a reference weight in an electronic scale with a drivable cam disc and a lever operable by said cam disc.
The sensitivity of precise scales is customarily checked from time to time by using a reference weight which is deposited on a carrier built into the weighing mechanism below the pan of the scale. If necessary, a correcting factor is determined which may be used to properly adjust the scale.
In the U.S. Pat. No. 4,425,975 (Swiss patent No. 650,337) the depositing of a U-shaped reference weight is accomplished by pulling a wedge from under a spring sheet carrying the reference weight. As a result, the reference weight is lowered and placed onto the carrier of the scale pan. The wedge is shifted forward and backward with a lever operable from outside of the scale housing. The disadvantage of this apparatus is that it is not suitable for the selective use of more than one weight.
European patent application No. A1-0,044,707 shows an apparatus for the depositing of one or more reference weights. In this device the reference weights are suspended on swivelable levers. The levers are supported on cam discs which are attached on a horizontally lying shaft. The shaft may be put into motion by hand or by means of a motor.
The reference weights are disposed loosely suspended in the rest position, as well as during adjustment of the scale. Because the weights are loosely suspended, damage may occur as a result of impacts during transportation operation of the scale. In the case of scales with a and large measuring range (0.5 kg and more) it is not possible to accommodate a reference weight corresponding to the maximum load of the scale below the scale pan.
The object of the present invention is to provide an apparatus with which reference weights may be deposited individually or jointly, and in which the reference weights, whenever they are not needed, do not strain the operating mechanism.